The application value of ¹⁸F-FDG PET/CT in patients with differentiated thyroid cancer of high thyroglobulin level and negative ¹³¹I whole body scan

Objective: To estimate the valuate of ¹⁸F-FDG PET/CT as a routine examination for the patients with suspected differentiated thyroid carcinoma (DTC) recurrence, accompanied by the increase of thyroglobulin (Tg) and negative ¹³¹I whole body scan. Method: 32 patients who suffered from DTC receiving post-operative ¹³¹I therapy, with increase of Tg and negative ¹³¹I whole body scan, were performed ¹⁸F-FDG PET/CT, and follow-up continued. Patients were divided into two groups according to the level of Tg:H group (Tg > 10 ng/ml) and L group (Tg < 10 ng/ml). Histopathological examination, ultrasound examination and clinical follow-up were used to verify the result, and assess the clinical value of PET/CT. Result: PET/CT imaging results indicated that among 32 patients, there were 20 positive (18 true-positive and 2 false-positive) and 12 negative (4 true-negative and 8 false-negative). Among 18 patients with true positive, 15 cases with local disease, 6 cases with distant metastasis, and 3 patients with both local invasion and distant metastasis. The overall sensitivity, specificity and accuracy were 69.2%, 66.7% and 68.8%, respectively. Compared with the L group, H group developed higher sensitivity (80% versus 33.3%), specificity (100% versus 60%) and accuracy (80.9% versus 45.5%). In 32 patients, 18 cases (56.2%) changed the strategies of clinical treatment, and 12 cases (37.5%) were received the radical operation under guidance. Conclusion: ¹⁸F-FDG PET/CT can detect and locate accurately for the regional metastasis and recurrence of patients with DTC, accompanied by the increase of serum Tg and negative ¹³¹I whole body scan. Therefore, it can be recommended as a routine diagnostic tool. (authors)